The stock of existing infrastructure (including buildings, bridges, tunnels, tanks, pipes, support structures in industrial facilities) is enormous. Financial and operational pressures necessitate that such infrastructure be continually maintained. Such maintenance often involves repair and strengthening of such structures or their individual members. In the past two decades surface mounted reinforcements have gained widespread acceptance for such repair and strengthening. These surface mounted reinforcing materials include, but are not limited to, fiber reinforced polymers (FRP), fiber reinforced cementitious matrices, fiber reinforced coatings as well as prefabricated panels utilizing a variety of materials.
Typically such surface mounted reinforcements are attached to existing structural surfaces by adhesion. The adhesives can include epoxies, vinyl esters, phenolic materials, cementitious materials etc. It is well understood that such surface mounted reinforcements can debond from the structural surfaces when the strains in the reinforcement material reach some threshold values. Such debonding failures are often sudden and catastrophic. In addition, such debonding failures occur at strength or strain values far below the available strength/strain of such surface mounted reinforcing materials, thus resulting in under-utilization of the full potential of such materials. Research has also demonstrated that such debonding failures can be mitigated or delayed by the use of anchors which tie the surface mounted reinforcements deeper into the structural members rather than relying on surface adhesion only. As such, several different types of anchors are currently being used in the industry. These anchors typically comprise raw fiber/rovings which are installed in drilled holes filled with adhesive and the free ends of the anchors are splayed onto the surface of the structural members.
For example, with reference to U.S. Pat. No. 7,574,840, a connector includes a roving, a borehole that pierces a first beam, backfill, and an adhesive. The roving is composed of a loosely twisted length of flexible filaments. The roving is inserted into a borehole with free ends of the roving protruding from borehole openings. A middle portion of the roving is disposed in the borehole. Backfill is added to the borehole to anchor the roving within the borehole. The backfill fluid fills the borehole and prevents the idle portion from being removed from the borehole. The two free ends of the roving are splayed so that the loose filaments are substantially separate. The splayed filaments are then attached to outer surfaces by an adhesive.
In another conventional application, as described in U.S. Patent Application Publication No. 2011/0036029, a construction reinforcement rod includes a polymer matrix of a reinforcement of elongated shape in lamellar form. The reinforcement matrix is introduced into a furnace, brought to a temperature suitable for leading to the pyrolysis of the polymer matrix of the reinforcement. After the polymer matrix is removed, the fibers/rovings are rearranged in a fan-like configuration.
The current state of practice vis-à-vis such anchors and connectors has several limitations:
1. Where the anchors are supplied by a manufacturer, the installer has to work with easily damageable fibers and rovings.
2. In many cases, the installers make their own anchors from rovings or folded woven FRP supplied by manufacturers in which case there can be considerable variability in the field-production of such anchors.
3. These flexible anchors, composed of rovings, are then installed into drilled holes filled with adhesive. Often a tool has to be used to insert the anchors into the adhesive-filled drilled holes. Since the rovings and fibers are flexible, there is no visual or other verification that the anchors have reached the required embedment depth or that they are not damaged in any way in the holes. After repeated use, the tools become very sticky and can pull the fibers/rovings out of the hole. This requires introducing possible hazardous chemicals to clean the tool and maintain the work quality.
4. Often engineering plans will call out either a diameter for the anchors or the diameter of the drilled hole within which these anchors are to be installed. In the first instance, since the anchors are composed of flexible fibers or rovings, it is very difficult for inspectors on the construction site to verify the anchor diameter per the plans. In the second instance it is impossible to verify if the anchors have the correct number of fibers/rovings to provide the required structural strength.
5. In some instances, engineering plans will actually provide a required strength that the anchors have to provide. In this case it is very difficult for installers or inspectors to know the rating for such anchors when they are ready to be installed in the field.
Therefore, it may be desirable to provide factory fabricated anchors and connectors with preformed and pre-cured reinforced portions for ease of diameter and/or length measurement. It may be desirable to provide anchors and connectors having a predetermined number of fibers or rovings based on design and testing to achieve certain capacity ratings. It may be desirable to provide preformed and pre-marked reinforced ends or midsections for ease of verification in the field, ease of installation (e.g., no or minimal tools required), and ease of verification of depth of embedment via marked lines. It may be desirable to provide anchors and connectors having listed anchor strengths with testing backup and/or complete reliability from design to manufacture to installation. It may be desirable to provide anchors and connectors installable via installation techniques similar to those for metallic anchors, which are conventionally used extensively in the industry, so as to create consistency and reduce errors in the field. It may be desirable to provide anchors and connectors with material traceability and/or delivered in clearly-labeled containers showing anchor type and, in some aspects, cross-linked with plans showing installation locations.